The present invention relates to a wood-type golf club head having a hollow interior, and more particularly a hollow wood-type golf club head having a spring effect suppressed without excessively increasing the weight of a face portion of the club head.
It has been recently set in golf rules that the design, material and/or construction of, or any treatment to, the club head must not have the effect of a spring which exceeds the limit set forth in the Pendulum Test Protocol on file with the R&A (upper limit: 239 μs+error of 18 μs). Simply put, the spring effect is an ability of a club face which depresses and then springs back into shape, when striking a ball, to act as a spring or trampoline, adding extra oomph to a shot.
However, in case that a large-sized hollow golf club head is formed from a metallic material having a high specific strength, the club head tends to have a spring effect which exceeds the limit set forth in the golf rules. Therefore, in order to produce golf club heads which meet the golf rules, it may be required hereinafter to further lower the spring effect.
The smaller the rigidity of a face portion of a club head, the larger the spring effect. Specifically, the smaller the thickness of the face portion or the smaller the Young's modulus of a metallic material constituting the face portion, the larger the spring effect of the club head tends to become. Therefore, assuming the use of metallic materials conventionally used for golf club heads, it is required for lowering the spring effect to increase the thickness of the face portion and to decrease the flexure of the face portion at ball striking. However, if the face portion is made thick, a margin of weight capable of using in weight distribution design of club heads is decreased, so the degree of freedom in design about position of the club head's center of gravity is decreased. Therefore, it is desired to lower the spring effect without increasing the thickness of face portion.
US 2007/0275792 A1 proposes disposing at least one stiffening member such as a mass member or a rib at a junction interconnecting a sole, a crown and a skirt to a striking face, thereby allowing a reduction in thickness of the striking face while maintaining a maximum coefficient of restitution of 0.830 or less per USGA rules.
It is an object of the present invention to provide a wood-type golf club head capable of easily controlling the spring effect within a range provided in the R&A rules without excessively increasing the weight of a face portion of the club head.
This and other objects of the present invention will become apparent from the description hereinafter.